Abstract 14039: Myocardial Work Efficiency is Reduced in Nonobstructive Hypertrophic Cardiomyopathy Patients With Exercise-Induced Symptoms

Abstract

Introduction: Despite normal ejection fraction, nonobstructive hypertrophic cardiomyopathy (nHCM; rest and provoked gradients <30 mmHg) is associated with high rates of angina, arrhythmias and heart failure symptoms, as well as abnormalities of echo-based myocardial strain. Using Myocardial Work (MW) analysis, we investigated the potential mechanisms contributing to exercise-induced symptoms in nHCM. Methods and Results: Using validated methods (EchoPAC), longitudinal strain and non-invasive blood pressure were integrated to generate normalized left ventricular pressure curves and pressure-strain loops to derive global and segmental MW data in 14 nHCM patients with normal ejection fraction (>55%) who underwent treadmill stress testing. Global myocardial work efficiency was expressed as the ratio of global constructive work over the sum of global constructive and wasted work. A total of 9 of 14 patients reported symptoms during exercise (chest pain, dyspnea, and palpitations) and this group had reduced global myocardial work efficiency compared to those without exercise-induced symptoms (85% vs 90%, respectively, p = 0.04, Figure 1). No statistical differences were noted in age, % men, maximal wall thickness, ejection fraction, E/e’ ratio, resting blood pressure, resting global strain and exercise performance between symptomatic and asymptomatic patients. Conclusions: Despite similar ventricular morphology, resting mechanics and exercise performance, nHCM patients with symptoms during exercise have worse myocardial work efficiency. Our data suggest that mechanisms potentially impacting global strain may be distinct from those affecting myocardial work efficiency. Understanding these differences may offer insights into management of exercise-induced symptoms.